First, power up the bike. Next, select a PAS level using the UP and DOWN arrows on the control for the bike's Display Panel "3" or "4" is ideal for learning how to use the Harmony control (located near the right handlebar grip).
The chrome button on top toggles between "Manual" and "Automatic" modes.
Manual mode shows an Orange scale....the fewer orange blips that are showing, the higher the gearing will be (and the faster the bike will go)....more orange blips mean a lower gear is selected, and the bike will have better hill-climbing power. This is adjusted by twisting the black grip that is part of the shifter.
Automatic mode shows a Blue scale. By twisting the black grip, you effectively set the "RPM" (aka "Cadence") you want to pedal at, and the system will adjust the gearing to keep you pedaling at that rate. Pedaling RPM is the rate at which you are turning the crank. For reference, the middle of the blue scale is set to approximately 70 RPM. Harmony is designed to keep RPM relatively constant by shifting gears as conditions change.